In recent years, e.g., a liquid crystal display device has been widely used for a liquid crystal television, a monitor, a portable telephone, etc. as a flat panel display having features such as a smaller thickness and a lighter weight compared to a conventional cathode ray tube. Such a liquid crystal display device includes a backlight device and a liquid crystal panel. The backlight device emits light and the liquid crystal panel displays a desired image by serving as a shutter with respect to light from a light source provided in the backlight device.
The backlight device has been provided as a sidelight type or a direct type in which a linear light source composed of a cold-cathode tube or a hot-cathode tube is located on the side or underside of the liquid crystal panel. However, the cold-cathode tube etc. contain mercury and have not been easily recyclable when they are discarded. Therefore, some conventional backlight devices use a mercury-free light-emitting diode (LED) as a light source (see, e.g., JP 2004-21147 A).
In the backlight device of the above first conventional example, three types of light-emitting diodes for emitting three colors (red (R), green (G), and blue (B)) of light are provided, and the light rays from the three types of light-emitting diodes are mixed into white light, which then is directed to the liquid crystal panel as illumination light.
In another conventional backlight device, white light-emitting diodes are provided in addition to the three types of R, G, and B light-emitting diodes (see, e.g., JP 2002-350846 A). This backlight device of the second conventional example is considered to be able to emit a neutral color of illumination light without reducing the brightness.